Main Controlling Factors and Experimental Study on Permeability of Coal-rock mass During Full Stress-strain Process

The experimental study on several key factors of coal specimen permeability is conducted herein. Permeability properties of coal specimens are analyzed systematically for different gas pressure, and different stress-strain conditions. Quantitative and qualitative relation between coal sample permeability and confining pressure, gas pressure and stress-strain curve is established respectively. The controlling mechanism and changing laws of permeability of coal samples under variable loading conditions are discussed. The results show that: for fixed gas pressure condition, coal permeability decreases with increasing of confining pressure; and the decreasing law obeys an exponential law; for fixed confining pressure condition, the relation between permeability and gas pressure is show a approximate "V" cure in shape affected by Klinkenberg effect; at the stage of micro fissure closing and elastic deformation, the permeability of coal specimen decreases with the increasing of stress; after entering into the yield stage, the permeability of coal specimen reaches the minimum and the anti-exceeding is accomplished before it reaching the peak strength.